title: Combined serum creatinine and cystatin C Schwartz formula predicts kidney function better than the combined CKD-EPI formula in children.
abstract: BACKGROUND
  The combined serum creatinine (SCreat) and cystatin C (CysC) CKD-EPI formula constitutes a new advance for glomerular filtration rate (GFR) estimation in adults. Using inulin clearances (iGFRs), the revised SCreat and the combined Schwartz formulas, this study aims to evaluate the applicability of the combined CKD-EPI formula in children.
  
  
  METHODS
  201 iGFRs for 201 children were analyzed and divided by chronic kidney disease (CKD) stages (iGFRs ≥90 ml/min/1.73 m(2), 90 > iGFRs > 60, and iGFRs ≤59), and by age groups (<10, 10-15, and >15 years). Medians with 95% confidence intervals of bias, precision, and accuracies within 30% of the iGFRs, for all three formulas, were compared using the Wilcoxon signed-rank test.
  
  
  RESULTS
  For the entire cohort and for all CKD and age groups, medians of bias for the CKD-EPI formula were significantly higher (p < 0.001) and precision was significantly lower than the solely SCreat and the combined SCreat and CysC Schwartz formulas. We also found that using the CKD-EPI formula, bias decreased and accuracy increased while the child age group increased, with a better formula performance above 15 years of age. However, the CKD-EPI formula accuracy is 58% compared to 93 and 92% for the SCreat and combined Schwartz formulas in this adolescent group.
  
  
  CONCLUSIONS
  The performance of the combined CKD-EPI formula improves in adolescence compared with younger ages. Nevertheless, the CKD-EPI formula performs more poorly than the SCreat and the combined Schwartz formula in pediatric population.
authors.affiliation: Division of Pediatric Nephrology, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: H
authors.initials: H
authors.lastname: Chehade
authors.forename: F
authors.initials: F
authors.lastname: Cachat
authors.forename: A-S
authors.initials: AS
authors.lastname: Jannot
authors.forename: B-J
authors.initials: BJ
authors.lastname: Meyrat
authors.forename: D
authors.initials: D
authors.lastname: Mosig
authors.forename: D
authors.initials: D
authors.lastname: Bardy
authors.forename: P
authors.initials: P
authors.lastname: Parvex
authors.forename: E
authors.initials: E
authors.lastname: Girardin
mesh_terms: D000293:Adolescent; D000465:Algorithms; D002138:Calibration; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007444:Inulin / Q000493:pharmacokinetics; D007668:Kidney / Q000187:drug effects* / Q000502:physiology*; D007676:Kidney Failure, Chronic / Q000188:drug therapy* / Q000503:physiopathology; D007677:Kidney Function Tests / Q000592:standards*; D008297:Male; D015203:Reproducibility of Results
chemical_list: D055316:Cystatin C; D007444:Inulin; D003404:Creatinine